Method and apparatus for aligning and/or leveling a test head

ABSTRACT

One embodiment of the present invention is a method for aligning a first workpiece to a second work piece that includes: (a) placing the first workpiece on an alignment apparatus including: (i) two or more fluid chambers disposed in fixed relation to each other, the chambers having a movable wall and one or more apertures for admitting or releasing fluid; (ii) fluid channels coupled to the one or more apertures that enable fluid to flow between at least two of the fluid chambers; and (iii) one or more valves disposed to enable or to stop the flow of fluid through one or more of the one or more fluid channels; (b) pumping incompressible fluid into the fluid chambers; (c) opening the one or more valves; (d) bringing the first and second workpieces into contact; (e) waiting a predetermined time for fluid flow in the fluid channels; (f) determining whether the first and second workpieces are aligned; (g) if they are aligned, shutting the valves; and (h) if they are not aligned, moving the second workpiece a predetermined amount in a predetermined direction, and returning to waiting.

This patent application is a divisional of a U.S. patent applicationhaving Ser. No. 11/708,517 that was filed on Feb. 20, 2007, which U.S.patent application is incorporated herein in its entirety.

TECHNICAL FIELD OF THE INVENTION

One or more embodiments of the present invention relate to method andapparatus for aligning and leveling a test head.

BACKGROUND OF THE INVENTION

Semiconductor components are used in the fabrication of electronic itemssuch as multichip modules. For example, bare semiconductor dice can bemounted to substrates such as printed circuit boards, and ceramicinterposers. Flip chip mounting of bumped dice is one method forelectrically connecting the dice to the substrates. With flip chipmounting, solder bumps on the device bond pads are reflowed intoelectrical contact with contacts on the substrate. Chip on board (COB)mounting of dice to substrates can also be employed. With chip on boardmounting, wire bonds are formed between the device bond pads andcontacts on the substrate.

Chip scale packages are sometimes used in place of bare dice forfabricating electronic items. Typically, a chip scale package includes asubstrate bonded to the face of a bare die. The substrate includesexternal contacts for making outside electrical connections to the chipscale package. The external contacts for one type of chip scale packageinclude solder balls arranged in a dense array such as a ball grid array(BGA) or a fine ball grid array (FBGA). In general, chip scale packagescan be mounted to substrates using the same mounting methods employedwith bare dice.

Besides making permanent electrical connections between semiconductorcomponents and substrates for fabricating multichip modules or otherpackaging applications, electrical connections are necessary for testingapplications. For example, bare dice are tested in the manufacture ofknown good dice (KGD). Chip scale packages must also be tested prior touse in electronic items. In these cases, electrical connections withdevice bond pads for bare dice, or with the external contacts for chipscale packages, are typically non-bonded, temporary electricalconnections.

In either packaging or testing applications, a substrate includescontacts that must be physically aligned with, and then electricallyconnected to, corresponding contacts on a component. As semiconductorcomponents become smaller, and contacts become denser, aligning andelectrically connecting components to substrates become more difficult.Accordingly, a design consideration in packaging and testing ofsemiconductor components is a method for aligning and connectingcomponents to mating substrates.

As such, one such problem facing the semiconductor industry is how toplanarize a probe card to a wafer during testing of individual die onthat wafer. During probe testing a probe card must be aligned and placedin electrical contact with a wafer. When the wafer and probe card aremoved together in a vertical direction, contacts on the wafer may notalways engage contacts on the probe card along the same plane. Suchmisalignment can cause pivoting of the wafer or the probe card. Also,the potential of misalignment can require overdriving the wafer or theprobe card in the vertical direction to make reliable electricallyconnections. This overdrive can damage contacts. In addition, ifplanarization is not achieved, then some probes may apply more pressureto corresponding lead pads on a die, while others may apply less. Thiscould result in incomplete electrical interfacing with the die so thatthe die tests bad, or that the lead pads to which more pressure isapplied are physically damaged—thereby making it impossible to use thedie in a finished product. Further, as the number of probes is increasedin probe apparatus, tilting becomes more of a problem.

Besides the above examples, alignment problems can occur in othersemiconductor packaging or assembly processes such as wire bonding andadhesive bonding of dice to leadframes. Another manufacturing processinvolving alignment occurs during fabrication of flat panel fieldemission displays (FEDs). An individual field emission display pixelincludes emitter sites formed on a baseplate. Electrons emitted by theemitter sites strike phosphors contained on a display screen to form animage. During fabrication of the field emission display it is necessaryto align the baseplate with the display screen. However, field emissiondisplays are typically constructed as a sealed package with a vacuumspace between the baseplate and the display screen. This spacecomplicates the alignment procedure because most alignment devices, suchas aligner bonder tools, are constructed to bring the mating componentsinto physical contact.

A need for alignment of a platen also arises in industries unrelated tosemiconductor testing; most importantly, in metal stamping and inprinting. The forces involved in these applications are relatively largein comparison to the forces involved in testing a semiconductor wafer,for example. Hydraulic cylinders have been used in variousconfigurations to support and level a platen involved in metal stampingand printing. Generally, the one or more hydraulic cylinders supportinga platen are relatively long, with a stroke that is comparable to orlarger than the bore. At the high forces and hydraulic pressuresinvolved in these applications, compressibility of the hydraulic fluidis a significant factor in determining the position and movement of theplaten as the press is actuated. Compression of the hydraulic fluid insupporting hydraulic cylinders is used as a cushion in high forcepresses that helps to level the loading of the press. As the influenceof compressibility of the hydraulic fluid increases with length of thecylinder, a long hydraulic cylinder is used to provide cushioning thatacts to level the platen under force. In certain configurations of theprior art, fluid is allowed to flow between hydraulic cylinders in apress in order to level the load. However, because of the length of thehydraulic cylinders used in presses, the cylinders are not an accuratemethod of setting the height of the platen. More accurate means areneeded to set and maintain alignment that are not sensitive to pressure,temperature, and loading.

In light of the above, there is a need in the art for method andapparatus that can align and level a substrate and a test head orelectronic components.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention satisfy one or more ofthe above-identified needs. In particular, one embodiment of the presentinvention is a method for aligning a first workpiece to a second workpiece that comprises: (a) placing the first workpiece on an alignmentapparatus comprising: (i) two or more fluid chambers disposed in fixedrelation to each other, the chambers having a movable wall and one ormore apertures for admitting or releasing fluid; (ii) fluid channelscoupled to the one or more apertures that enable fluid to flow betweenat least two of the fluid chambers; and (iii) one or more valvesdisposed to enable or to stop the flow of fluid through one or more ofthe one or more fluid channels; (b) pumping incompressible fluid intothe fluid chambers; (c) opening the one or more valves; (d) bringing thefirst and second workpieces into contact; (e) waiting a predeterminedtime for fluid flow in the fluid channels; (f) determining whether thefirst and second workpieces are aligned; (g) if they are aligned,shutting the valves; and (h) if they are not aligned, moving the secondworkpiece a predetermined amount in a predetermined direction, andreturning to waiting.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A shows a cross-sectional view of an alignment apparatus that isfabricated in accordance with one or more embodiments of the presentinvention, the alignment apparatus is shown prior to alignment of a testhead with a wafer;

FIG. 1B shows a cross-sectional view of the alignment apparatus shown inFIG. 1A in use after alignment of the test head with the wafer;

FIG. 1C shows a top sectional view of the alignment apparatus shown inFIG. 1A, which section is taken in a plane indicated by arrows A and A′of FIG. 1B;

FIGS. 2A-2C show top views of alignment apparatus that are fabricated inaccordance with one or more embodiments of the present invention;

FIG. 3 shows a flow chart of a method for aligning a test head inaccordance with one or more embodiments of the present invention;

FIGS. 4A-4C show partial cross-sectional views of alternativeembodiments of fluid chambers that may be used to fabricate one or moreembodiments of the present invention;

FIGS. 5A-5B show a cross-sectional view and a top sectional view,respectively, of an alignment and leveling apparatus that is fabricatedin accordance with one or more embodiments of the present invention inwhich pneumatic actuators are used to level a test head;

FIG. 6A shows a sectional perspective view of the alignment and levelingapparatus shown in FIG. 5A;

FIG. 6B shows an exploded assembly view, in perspective, of thealignment and leveling apparatus shown in FIG. 5A;

FIG. 7 shows a schematic drawing of the alignment and leveling apparatusshown in FIG. 5A, which drawing is used to help describe its operation;

FIG. 8 shows a flow chart of a method for aligning and leveling a testhead in accordance with one or more embodiments of the present inventionusing the alignment and leveling apparatus shown in FIG. 5A;

FIG. 9A is a cross-sectional view of an alignment and leveling apparatusthat is fabricated in accordance with one or more embodiments of thepresent invention for aligning and leveling a test head comprising ofmultiple segments;

FIG. 9B is a top sectional view of the alignment and leveling apparatusshown in 9A;

FIG. 9C is a cross-sectional view of the alignment and levelingapparatus shown in FIG. 9A in a locked configuration; and

FIG. 9D is a top sectional view of the alignment and leveling apparatusshown in 9C.

DETAILED DESCRIPTION

FIG. 1A shows a cross-sectional view of alignment apparatus 1000 that isfabricated in accordance with one or more embodiments of the presentinvention. In accordance with one or more such embodiments, alignmentapparatus 1000 may be utilized, for example and without limitation, asan apparatus for aligning a test head such as, for example and withoutlimitation, a wafer probe test head, a thermal contactor test head, amechanical measurement test head, an optical test head, an array ofelectrical contacts test head, and a multiplicity of any of such testheads.

As shown in FIG. 1, alignment apparatus 1000 comprises support plate1010 in which a multiplicity of reservoirs or chambers, for example andwithout limitation, four reservoirs 1020 ₁-1020 ₄ are arrayed(reservoirs 1020 ₁-1020 ₄ are seen in FIG. 1C, and a cross-section ofreservoirs 1020 ₁-1020 ₂ is seen in FIGS. 1A and 1B). As shown in FIG.1C, and in accordance with one or more embodiments of the presentinvention, reservoirs 1020 ₁-1020 ₄ are arrayed in a fixed relationshipwith respect to each other. In particular, reservoirs 1020 ₁-1020 ₄ aredisposed symmetrically about vertical central axis 1300 of support plate1010. In addition, and in accordance with one or more such embodimentsof the present invention, reservoirs 1020 ₁-1020 ₄ are arrayed in aplane on support plate 1010.

In accordance with one or more embodiments of the present invention,each of reservoirs 1020 ₁-1020 ₄ includes a bottom surface and a topsurface (top surfaces 1030 ₁-1030 ₂ are shown in FIG. 1A) that includesa movable portion. In accordance with one or more such embodiments, topsurfaces 1030 ₁-1030 ₂ are movable and include diaphragms made, forexample and without limitation, of thin embossed sheets of type 316Lstainless steel. Further, in accordance with one or more suchembodiments, one or more pillars are mechanically connected (for exampleand without limitation, rigidly connected) to top surfaces 1030 ₁-1030 ₂of reservoirs 1020 ₁-1020 ₂ (as shown in FIG. 1A, pillars 1040 ₁-1040 ₂are mechanically connected to top surfaces 1030 ₁-1030 ₂). In accordancewith one or more such embodiments, pillars 1040 ₁-1040 ₂ may be anysuitable material such as, for example and without limitation, a metalsuch as type 304 stainless steel, hardened tool steel, titanium, and thelike. Pillars 1040 ₁-1040 ₂ support test head 3000, and thereby,determine its orientation with respect to support plate 1010. Inaccordance with one or more embodiments of the present invention,pillars 1040 ₁-1040 ₂ may be attached to top surfaces 1030 ₁-1030 ₂ bymeans of, for example and without limitation, mechanical fasteners,posts, magnetic force, adhesives, or vacuum.

FIG. 1C shows a top sectional view of alignment apparatus 1000, whichsection is taken in a plane indicated by arrows A and A′ of FIG. 1B. Asshown in FIG. 1C, and in accordance with one or more embodiments of thepresent invention, each of reservoirs 1020 ₁-1020 ₄ has an aperture thatadmits and releases fluid, which apertures are connected to fluidchannels that are interconnected at junction 1400. Thus, in accordancewith one or more such embodiments, as shown in FIG. 1A, fluid may flow:(a) from reservoir 1020 ₂, through the aperture therein; (b) throughfluid channel 1050 ₂; (c) past junction 1400; (d) through fluid channel1050 ₁; and (e) into reservoir 1020 ₁, through the aperture therein. Inaddition, as shown in FIGS. 1A and 1B, and in accordance with one ormore embodiments of the present invention, alignment apparatus 1000includes valve mechanism 1600 (for example and without limitation, asolenoid-operated, spring-return valve) that is adapted to stop the flowof fluid in alignment apparatus 1000. In particular, as shown in FIGS.1A and 1B, valve mechanism 1600 is affixed to support plate 1010 byscrews (not shown), and sealed against fluid leaks by O-rings 1601 and1602. Valve mechanism 1600 includes plug 1620 which is urged upward in avertical direction by spring 1630, and may be urged in a downwardvertical direction by activation of electromagnet 1610 by a controller(not shown). Such a controller may be fabricated readily by one ofordinary skill in the art utilizing, for example and without limitation,any one of a number of commercially available programmablemicroprocessors, which microprocessors may be programmed routinely andwithout undue experimentation utilizing any one of a number of methodsthat are also well known to those of ordinary skill in the art. Inaccordance with one or more such embodiments, plug 1620 may be one ormore of a metal, a plastic-coated ferromagnetic metal impregnatedplastic, a glass-filled PTFE polymer, a PEEK polymer, a PFA-coatedalnico magnet, and so forth. In accordance with one or more embodimentsof the present invention, plug 1620 may have a relief hole along an axisthrough the plug which is designed to allow fluid flow from a top cavityto a bottom cavity in which plug 1620 moves in an upward and downwardmotion.

In accordance with one or more embodiments of the present invention, thefluid used in alignment apparatus 1000 may be a gas or a liquid such as,for example and without limitation, a hydraulic fluid. More preferably,the fluid is a relatively incompressible liquid such as, for example andwithout limitation, silicone vacuum pump oil, aliphatic oil, and varioushydraulic fluids.

In addition, in accordance with one or more embodiments of the presentinvention, alignment apparatus 1000 includes a pump (not shown) to pumpfluid into reservoirs 1020 ₁-1020 ₄ from a fluid reservoir (not shown).Such a fluid replenishment system may further include a pressure reliefvalve and a check valve. The pressure relief valve ensures that anyexcess fluid pressure is returned to the system fluid reservoir. Inaccordance with one or more embodiments of the present invention, thepump may be any suitable pump such as, for example and withoutlimitation, a piezoelectric pump, a peristaltic pump, or a contractionof a bladder. In accordance with one or more such embodiments, the pumpmay pump fluid into a fluid channel at common junction 1400 or into anyof the fluid channels individually. Alternatively, each of chambers 1020₁-1020 ₄ may be connected to a fluid reservoir.

In accordance with one or more embodiments of the present invention, avolume, including a cross sectional area and height of a reservoir maybe determined routinely and without undue experimentation by one ofordinary skill in the art in light of a particular application takinginto account one or more of the following: a force needed to be applied(for example to engage a test head with a wafer); a predetermined timefor fluid to flow among the reservoirs; and a viscosity of the fluidutilized.

FIGS. 2A-2C show top sectional views of alignment apparatus that arefabricated in accordance with one or more embodiments of the presentinvention. FIG. 2A shows a top sectional view of an embodiment of thepresent invention which comprises three reservoirs 2000 ₁-2000 ₃wherein: fluid channel 2010 ₁ having valve 2020 ₁ is connected betweenreservoirs 2000 ₁ and 2000 ₂; fluid channel 2010 ₂ having valve 2020 ₂is connected between reservoirs 2000 ₂ and 2000 ₃; and fluid channel2010 ₃ having valve 2020 ₃ is connected between reservoirs 2000 ₃ and2000 ₁. In accordance with such an embodiment, closure of all valves2020 ₁-2020 ₃ is required to stop the flow of fluid in the alignmentapparatus. FIG. 2B shows a top sectional view of an embodiment of thepresent invention which comprises four reservoirs 2100 ₁-2100 ₄ wherein:fluid channel 2110 ₁ having valve 2120 ₁ is connected between reservoirs2100 ₁ and 2100 ₃; and fluid channel 2110 ₂ having valve 2120 ₂ isconnected between reservoirs 2100 ₂ and 2100 ₄. In accordance with suchan embodiment, closure of all valves 2120 ₁-2120 ₂ is required to stopthe flow of fluid in the alignment apparatus. Lastly, FIG. 2C shows atop sectional view of an embodiment of the present invention whichcomprises five reservoirs 2200 ₁-2200 ₅ wherein: fluid channels 2210₁-2210 ₅ having valves 2220 ₁-2220 ₅, respectively, all meet at a commonjunction. In accordance with such an embodiment, closure of all valves2220 ₁-2220 ₅ is required to stop the flow of fluid in the alignmentapparatus. Thus, as one can readily appreciate from this, embodiments ofthe present invention exist in many variations, for example and withoutlimitation, an embodiment having four reservoirs where each of the fourreservoirs may have fluid channels connecting each of the fourreservoirs with an opposite chamber so that fluid may fluidtherebetween. In addition, and in accordance with one or more suchembodiments, each reservoir may connect to a fluid channel that connectseach reservoir to a common point or junction. Further, in accordancewith one or more such embodiments, each fluid channel may have a fluidvalve that is capable of stopping a flow of liquid to or from eachreservoir, and there may be a fluid valve at a common point or junctionof all the fluid channels.

Referring back to FIGS. 1A-1C, in accordance with one or more furtherembodiments of the present invention, pillars 1040 ₁-1040 ₄ are notutilized, and reservoirs 1020 ₁-1020 ₄ may include bellows that protrudeabove the surface of support plate 1010. Further, in accordance with oneor more further embodiments of the present invention, reservoirs 1020₁-1020 ₄ may include pistons that may be activated to provide aninitialization state wherein each reservoir has the same volume of fluidtherein, which pistons would operate under the control of a controller(not shown). Such a controller may be fabricated readily by one ofordinary skill in the art utilizing, for example and without limitation,any one of a number of commercially available programmablemicroprocessors, which microprocessors may be programmed routinely andwithout undue experimentation utilizing any one of a number of methodsthat are also well known to those of ordinary skill in the art.

FIG. 3 shows a flow chart of a method for aligning a test head inaccordance with one or more embodiments of the present invention. Asshown in FIG. 3, at step 5000, alignment apparatus 1000 is initializedby a controller which causes fluid to be pumped from a reservoir (notshown) into reservoirs 1020 ₁-1020 ₄. Such a controller may befabricated readily by one of ordinary skill in the art utilizing, forexample and without limitation, any one of a number of commerciallyavailable programmable microprocessors, which microprocessors may beprogrammed routinely and without undue experimentation utilizing any oneof a number of methods that are also well known to those of ordinaryskill in the art. Then, control is transfer to step 5010.

At step 5010 shown in FIG. 3, the controller sends a signal that causesvalve mechanism 1600 to open to enable fluid flow in fluid channels 1050₁-1050 ₄. Then, control is transferred to step 5020.

At step 5020 shown in FIG. 3, wafer 4000 is mounted in a conventional,movable chuck (not shown) that is capable of moving in a verticaldirection in response to control signals sent by the controller. Next,the controller sends a signal that causes wafer 4000 to be moveddownward to touch test head 3000, as detected, for example and withoutlimitation, by electrical contact between probes on test head 3000 andwafer 4000. The controller also delays, by a predetermined amount, toallow fluid flow in fluid channels 1050 ₁-1050 ₄. Then, control istransferred to step 5030.

At step 5030 shown in FIG. 3, the controller carries out a test todetermine whether wafer 4000 and test head 3000 are aligned in anorientation in which a bottom surface of wafer 4000 is parallel to a topsurface of probe head 3000, such alignment test being carried out, forexample and without limitation, by the controller's examining a map ofelectrical contacts made between an array of probes on test head 3000and wafer 4000. Then, control is transferred to decision step 5040.

At decision step 5040, the controller determines whether wafer 4000 andtest head 3000 are aligned. If they are aligned, control is transferredto step 5070, otherwise; control is transferred to step 5050.

At step 5050 shown in FIG. 3, the controller sends a signal that causeswafer 4000 to be moved downward by a predetermined amount. Then, controlis transferred to step 5060.

At step 5060 shown in FIG. 3, the controller delays by a predeterminedamount to allow fluid to flow in fluid channels 1050 ₁-1050 ₄. Then,control is transferred to step 5030.

At step 5070, the controller sends a signal that causes valve mechanism1600 to stop fluid flow in fluid channels 1050 ₁-1050 ₄. Then, controlis transferred to step 5080 where the process ends.

As one of ordinary skill in the art will readily appreciate from theabove, test head 3000 may be a planar test head or test head 3000 maycomprise test pins that are projected up and in a plane. In general,test head 3000 may be a first workpiece and wafer 4000 may be a secondworkpiece. Further, as wafer 4000 and test head 3000 are urged intocontact, test head 3000 generates forces on each of reservoirs 1020₁-1020 ₄. These forces cause fluid to flow in fluid channels 1050 ₁-1050₄ between reservoirs 1020 ₁-1020 ₄ and junction 1400. If more force isapplied to one of reservoirs 1020 ₁-1020 ₄ than others of reservoirs1020 ₁-1020 ₄, then fluid will flow from the one chamber to otherchambers. As this occurs, the top surface of the one chamber willsubside and the top surface of the other chambers will rise. The speedat which this occurs will be determined by the rate of fluid flow influid channels 1050 ₁-1050 ₄ and the surface area of reservoir tops 1030₁-1030 ₄. In this manner, reservoirs 1020 ₁-1020 ₄ will enable test head3000 to adjust for aplanarity of wafer 4000 or for alignment of testhead 3000 with wafer 4000. When alignment has been achieved, fluid flowin the fluid channels is halted by closing the valves, thereby lockingtest head 3000 in a fixed orientation with respect to wafer 4000.

In accordance with one or more alternative embodiments of the presentinvention, test head 3000 may be leveled or aligned by applying a forceto change the amount of fluid contained in one or more of reservoirs1020 ₁-1020 ₄, wherein the force may be applied using one or more of amagnetic mechanism, a pneumatic mechanism, and a spring mechanism.

In accordance with one or more embodiments of the present invention, afluidic chamber may be configured to have a movable side that dependsupon the specific requirements of the application. By way of example,FIGS. 4A-C are partial cross-sectional views of fluidic chambers thatmay be used to fabricate one or more embodiments of the presentinvention, the fluidic chambers having different configurations. Inparticular, FIG. 4A shows a cross-sectional view of fluidic chamber 100having movable pillar 200 attached to test head 3000 by means ofthreaded bolt 300. As shown in FIG. 4A, movable pillar 200 comprises twopillars having a bridge connecting them. As further shown in FIG. 4A,bolt 300 is attached from a bottom side of movable pillar 200 to enableeasy dismounting of test head 3000 (i.e., an attachment mechanism isformed by bolt 300 being threaded through movable pillar 200 and testhead 3000). As still further indicated by FIG. 4A, diaphragm 400 is anannulus attached to movable pillar 200 at an inner diameter edge and atan outer diameter edge. In addition, as shown in FIG. 4A, movable pillar200 is attached to a top surface of diaphragm 400 on an area betweenundulation 410 proximal to an inner diameter of diaphragm 400 andundulation 420 proximal to an outer diameter of diaphragm 400. Fluidpressure in chamber 100 of FIG. 4A bows diaphragm 400 upward, therebyurging movable pillar 200 and attached test head 3000 in upwarddirection. As further shown in FIG. 4A, fluid chamber 100 is connectedto shut-off valve 500 by fluid channel 450. Whenever valve 500 in fluidchannel 450 is open, fluid is able to flow from annular chamber 100 toother similar fluid chambers (not shown). Whenever valve 500 is closed,as shown in FIG. 4A, fluid in annular chamber 100 is fixed, therebyholding movable pillar 200 and attached portion of test head 3000 in afixed vertical position.

In order that the attached portion of test head 3000 be held in a fixedposition that is substantially unchanged by downward pressure on testhead 3000, in accordance with one or more embodiments of the presentinvention, fluid chamber 100 is preferably filled with a relativelyincompressible fluid such as, for example and without limitation,silicone vacuum pump oil, aliphatic oil, and the like. In accordancewith one or more further such embodiments, fluid chamber 100 has aheight in a vertical direction that is less than a maximum diameter offluid chamber 100 in a horizontal direction. In particular, inaccordance with one or more such embodiments, fluid chamber 100 has aheight in the vertical direction that is less than 10% of a maximumdiameter of fluid chamber 100 in a horizontal direction, therebyreducing vertical deflection of test head 3000 due to compressibility offluid in fluid chamber 100. Alternatively, in accordance with one ormore such embodiments, fluid chamber 100 encloses a volume of fluid thatis less than 1/10 times an area of moveable wall 400 raised to a power3/2.

In accordance with one or more embodiments of the present invention,test head 3000 may be supported on two or more posts that are attacheddirectly to fluid chambers of the type (i.e., fluid chamber 100) shownin FIG. 4A. In addition, in accordance with one or more embodiments, apost supporting test head 3000 may be rigidly attached to movable pillar200, wherein mechanical means exist for adjusting a height of the post.By way of example, and as has been described above, test head 3000 maybe supported on posts including one post that has a height that isadjustable by a screw mechanism; and two or more posts (comprising legsof movable pillar 200 shown in FIG. 4A) that are each attached to amovable wall (wall 400 shown in FIG. 4A) of a fluid chamber (forexample, fluid chamber 100 shown in FIG. 4A).

FIG. 4B shows a cross-sectional view of a fluidic chamber that may beused to fabricate one or more embodiments of the present invention,which fluidic chamber enables positioning of a test head in a horizontalplane as well as leveling in a vertical direction. As shown in FIG. 4B,fluid chamber 650 is formed by horizontal support plate 600, expandablebellows structure 610, plate 620, and movable plate 615 which is affixedto test head 3000. In accordance with one or more such embodiments ofthe present invention, expandable bellows structure 610 enables movableplate 615 to have a limited amount of movement in a horizontal directionas well as in a vertical direction. As further shown in FIG. 4B, testhead 3000 is urged upwardly by a force generator comprising Bellevillespring 630 that thrusts ball 640 against a center portion of test head3000. In operation, Belleville spring 630 is initially put in atensioned state by introducing fluid under pressure from an externalsource (not shown) into the fluid chambers, including fluid chamber 650shown in FIG. 4B, that support test head 3000, thereby urging movableplate 615 and attached test head 3000 in a downward direction. After theinitial tensioning of Belleville spring 630, the external source offluid pressure is sealed off from a network of fluid channels connectingthe fluid chambers, i.e., the network is thereby made closed. Then, testhead 3000 shown in FIG. 4B is aligned as described above in conjunctionwith FIG. 1A. In particular, the fluid valve or valves in channelsconnecting the chambers is opened (for example, valve 660 shown in FIG.4B), and a test piece is urged downwardly against test head 3000,thereby causing fluid to flow in channels interconnecting the fluidchambers to enable test head 3000 to come into parallel registrationwith respect to the test piece. The valve or valves in the fluidchannels (for example, valve 660 shown in FIG. 4B) are closed when testhead 3000 is in registration with the test piece, as determined, forexample and without limitation, by electrical contact patterns, byinterferometer measurements, by optical measurements, or by use of anyother means that are well known by one of ordinary skill in the art.After the valves are closed, an upward force of Belleville spring 630 ontest head 3000 urges movable plate 615 upward in a vertical direction,thereby maintaining a positive fluid pressure in the chambers. It willbe understood by one of ordinary skill in the art that a negative fluidpressure in the fluid chambers may also be used, wherein a spring orother mechanical force generator is employed to urge test head 3000downward toward support plate 620, thereby urging movable plate 615downward and bellows structure 610 to expand downwardly.

In accordance with one or more embodiments of the present invention, andas indicated in FIG. 4B, test head 3000 is aligned in a first horizontaldirection by alignment screw 670 that urges test head 3000 horizontallytoward the right. Other alignment screws (not visible in FIG. 4B) urgetest head 3000 in a second horizontal direction, preferably orthogonalto the first direction, and thereby may be used to urge test head 3000in a rotational direction around a vertical axis. In accordance with oneor more such embodiments, bellows structure 610 of each fluid chamber issufficiently flexible to allow horizontal movement necessary to aligntest head 3000 in a desired horizontal direction.

FIG. 4C shows a cross-sectional view of fluidic chamber 700 that may beused to fabricate one or more embodiments of the present invention. Asshown in FIG. 4C, chamber 700 includes movable piston 710 that is sealedat a perimeter of chamber 700 by O-ring 720. Further, piston 710includes post 715 which supports test head 3000. In accordance with oneor more embodiments of the present invention, test head 3000 may rest onpost 715 or it may be connected thereto, for example and withoutlimitation, by adhesives. As further shown in FIG. 4C, fluid channel 730passes through solenoid-operated, spring-return valve 740 (shown in aclosed position in FIG. 4C), where solenoid-operated, spring-returnvalve 740 is sealed to support plate 705 by O-rings 735 using, forexample and without limitation, screws (not shown).

One or more embodiments of the present invention are capable of aligninga test head to be parallel to a test piece without the need for contacttherebetween. In order to do this, a test head is connected to movablewalls of fluid chambers while fluid is able to flow in channelsinterconnecting the fluid chambers. Then, a force is applied to the testhead using, for example and without limitation, pneumatic actuators,springs, electromagnetic actuators, magnets, and hydraulic actuators. Inaccordance with one or more such embodiments, the force acts to changean orientation of the test head. FIG. 5A shows a cross-sectional view ofalignment and leveling apparatus 1500 that is fabricated in accordancewith one or more embodiments of the present invention wherein pneumaticactuators are used to align a test head. In accordance with one or moresuch embodiments, alignment and leveling apparatus 1500 may be utilizedto level a test head and to align it to a horizontal orientation.

FIG. 5A shows a cross-sectional view of alignment and leveling apparatus1500; FIG. 5B shows a top sectional view of alignment and levelingapparatus 1500 where the section is taken in a plane indicated by arrowsB and B′ of FIG. 5B; FIG. 6A shows a sectional perspective view ofalignment and leveling apparatus 1500; and FIG. 6B shows an explodedassembly view in perspective of alignment and leveling apparatus 1500.

In accordance with one or more embodiments of the invention, test head3000 is supported on four studs 1530 ₁-1530 ₄ that are aligned inpredetermined directions along an x-axis and a y-axis (studs 1530 ₁-1530₂ are shown in FIG. 5A). Each of four studs 1530 ₁-1530 ₄ is held in acorresponding post (posts 1540 ₁-1540 ₂ are shown in FIG. 5A, and posts1540 ₁-1540 ₄ are shown in FIG. 6B) attached to spider plate 1510 thatspans the distance between posts 1540 ₁-1540 ₄ and links posts 1540₁-1540 ₄ together. In accordance with one or more such embodiments, eachof studs 1530 ₁-1530 ₄ is held fast within a hole in a correspondingpost and is fastened to the post by a set screw (not shown); other meanssuch as a magnetic clamp, an electromagnetic clamp, a shape memory alloyclamp, a vacuum clamp, a press fit, and the like may be used to fastenthe stud to the post. In addition, and in accordance with one or moresuch embodiments, each of posts 1540 ₁-1540 ₄ is connected or attachedto movable walls 1550 ₁-1550 ₄ (movable walls 1550 ₁-1550 ₂ are shown inFIG. 5A) of a corresponding one of fluid chambers 1560 ₁-1560 ₄ (fluidchambers 1560 ₁-1560 ₂ are shown in FIG. 5A). In further addition, andin accordance with one or more such embodiments, each of fluid chambers1560 ₁-1560 ₂ contains silicone vacuum pump oil; alternatively thechambers may be filled with a fluid including mineral oil, hydraulicfluid, and the like which will remain fluid over a range of temperaturesexperienced by test head 3000. In still further addition, and inaccordance with one or more such embodiments, each of fluid chambers1560 ₁-1560 ₄ is connected by fluid channels 1570 ₁-1570 ₄ (fluidchannels 1570 ₁-1570 ₂ are shown in FIG. 5A) to common junction 1580which may be closed by solenoid-operated, spring-return valve 1700. Asshown in FIG. 5A, valve 1700 is sealed to support plate 1730 usingO-rings 1710-1720.

In accordance with one or more embodiments of the present invention,during a leveling and aligning process, fluid is free to flow in fluidchannels 1570 ₁-1570 ₄ that interconnect fluid chambers 1560 ₁-1560₄—-central valve 1700 is shown in an open position in FIG. 5A to allowfluid to flow therethrough. In accordance with one or more suchembodiments, fluid flows in the network of fluid channels 1570 ₁-1570 ₄to bring pressure within fluid chambers 1560 ₁-1560 ₄ into equilibrium.In particular, a downward force applied to one post causes fluid to fromthe fluid chamber attached to the one post, through channels to theother chambers, thereby acting to tilt test head 3000 downward on a sideattached to the one post. Likewise, an upward force on one post acts totilt test head 3000 upward on a side attached to the one post. Aftertest head 3000 is brought into alignment, shut-off valve 1700 is closedby releasing a magnetic force applied by solenoid 1750 on poppet 1740,thereby trapping fluid within each of fluid chambers 1560 ₁-1560 ₄ andfixing the vertical position of each of movable walls 1550 ₁-1550 ₄ ofeach of fluid chambers 1560 ₁-1560 ₄ and locking the orientation of testhead 3000 attached thereto.

As shown in FIG. 6A, and in accordance with one or more embodiments ofthe present invention, a force generator applies a downward force tospider plate 1510 and to attached posts 1540 ₁-1540 ₄, thereby urgingeach of movable walls 1550 ₁-1550 ₄ attached thereto downward so as tomaintain a fluid pressure within each of fluid chambers 1560 ₁-1560 ₄.In accordance with one or more embodiments of the present invention, theforce generator comprises: Belleville spring 1810 which is held incompression by central screw attachment 1820 (central screw attachment1820 is screwed into support plate 1835) so as to apply downward forceto spider plate 1510 and to attached posts 1540 ₁-1540 ₄, thereby urgingeach of movable walls 1550 ₁-1550 ₄ attached thereto downward. Inaccordance with one or more such embodiments, a baseline of fluidpressure is set by adjustment of screw 1820 so as to reduce theoccurrence of bubbles in the fluid, for example and without limitation,silicone oil, due to evolution of dissolved gas. Advantageously,Belleville spring 1810 applies a downward pressure to spider plate 1510without hindering the tilting motion necessary for alignment of testhead 3000.

As shown in FIG. 5A, and in accordance with one or more embodiments ofthe present invention, alignment and leveling apparatus 1500 comprisesfour force generators that are upwardly movable so as to engage a bottomsurface of test head 3000. In accordance with one or more embodiments ofthe present invention, the four force generators comprise fourpneumatically activated bosses 1830 ₁-1830 ₄ (bosses 1830 ₁-1830 ₂ areshown in FIG. 5A, and bosses 1830 ₁-1830 ₄ are shown in FIG. 6B) thatare upwardly movable so as to engage a bottom surface of test head 3000.Air pressures P_(X2), P_(X1), P_(Y1) and P_(Y2) are supplied to four airpockets 1840 ₁-1840 ₄, respectively, in support plate 1835, the top ofeach pocket being sealed by an expandable diaphragm (i.e., diaphragms1850 ₁-1850 ₄ where diaphragms 1850 ₁-1850 ₂ are shown in FIG. 5A, anddiaphragms 1850 ₁-1850 ₄ are shown in FIG. 6B) upon which a boss ismounted (air pockets 1840 ₁-1840 ₄ and diaphragms 1850 ₁-1850 ₄ may bereferred to below as pressure actuators 1890 ₁-1890 ₄). As shown in FIG.5B, and in accordance with one or more such embodiments, air atpressures P_(X2), P_(X1), P_(Y1) and P_(Y2) are applied as input tonozzles 1870 ₁-1870 ₄, respectively, from sources of pressurized air(not shown), and channels 1880 ₁-1880 ₄ connect nozzles 1870 ₁-1870 ₄ toair pockets 1840 ₁-1840 ₄.

In accordance with one or more such embodiments of the presentinvention, each boss may be moved independently by control of airpressure in a corresponding pocket under the boss. For example, a bossmay be moved vertically by air pressure so as to contact a back side oftest head 3000 and to urge test head 3000 to tilt upward on a sideproximal to the boss. After the alignment process is complete, airpressure in each pocket may be released, thereby allowing each boss toretract downward, and out of contact with test head 3000.

A process of aligning and leveling a test head in accordance with one ormore embodiments of the present invention may be better understood byreference to FIG. 7 (which is a schematic drawing of alignment andleveling apparatus 1500 shown in FIG. 5A) and to FIG. 8 (which is a flowchart of a method for aligning and leveling test head 3000 in accordancewith one or more embodiments of the present invention using alignmentand leveling apparatus 1500). For simplicity of exposition in FIG. 7,test head 6000 is represented as having arms X₁ and X₂ disposed along anx-axis and arms Y₁ and Y₂ disposed along a y-axis, the remainder of testhead 6000 being cut away to show the pneumatic actuators and the fluidicchambers of alignment and leveling apparatus 1500 (wherein the pneumaticactuators and the fluidic chambers are each being represented as afluidic cylinder for of ease of understanding the following).

As shown in FIG. 8, at step 7000, the process of leveling test head 6000begins by having controller 6010 cause an equal pressure to be appliedto each of pneumatic actuators 1890 ₁-1890 ₄ (i.e., this initializes theforce in the force generators) To do this, pneumatic switches 1910₁-1910 ₄ are activated by having controller 6010 apply a voltage to eachof the solenoids that control pneumatic switches 1910 ₁-1910 ₄, and byhaving controller 6010 apply equal control voltages V_(X1), V_(Y1),V_(X2), and V_(Y2) to each of electronically-controlled, pressureregulators 1920 ₁-1920 ₄. As a result, air pressures ofP_(X1)=P_(Y1)=P_(X2)=P_(Y2) are applied to pneumatic actuators 1890₁-1890 ₄, thereby moving bosses 1830 ₁-1830 ₄ connected to pneumaticactuators 1890 ₁-1890 ₄, respectively, upward into contact with testhead 6000. Next, an electronic counter associated with controller 6010is reset to i=0. Then, control is transferred to step 7010. Such acontroller may be fabricated readily by one of ordinary skill in the artutilizing, for example and without limitation, any one of a number ofcommercially available programmable microprocessors, whichmicroprocessors may be programmed routinely and without undueexperimentation utilizing any one of a number of methods that are alsowell known to those of ordinary skill in the art.

At step 7010 shown in FIG. 8, a position of test head 6000 is unlockedby causing controller 6010 to send signals to shut-off valves 1930₁-1930 ₄ disposed in fluid channels 1570 ₁-1570 ₄ interconnecting fluidchambers 1560 ₁-1560 ₄, thereby allowing fluid to flow therebetween (inaccordance with the embodiments described here, each fluid channel has avalve). Shut-off valves 1930 ₁-1930 ₄ are opened by having controller6010 apply a voltage to solenoids operating shut-off valves 1930 ₁-1930₄. For clarity of exposition, shut-off valves 1930 ₁-1930 ₄ shown inFIG. 7 are shown as being operated by separate solenoids, whereas infurther embodiments, the solenoids may be consolidated into a singlesolenoid. Whenever shut-off valves 1930 ₁-1930 ₄ are held open, anupward force on one side of test head 6000 near arm Y₁ will cause fluidto flow into the chamber disposed thereunder and the side proximal toarm Y₁ to move upward. Then, control is transferred to step 7020.

At step 7020 shown in FIG. 8, i.e., after unlocking the position of testhead 6000, an X-level is sensed by, for example and without limitation,a pattern of electrical contacts arrayed between a surface of test head6000 and a surface of a work piece (not shown). Then, control istransferred to decision step 7030.

At decision step 7030 shown in FIG. 8, electronic decision-makingcircuitry in controller 6010 branches depending on whether the sensedX-level indicates that a position of arm X₁ is higher than, lower than,or equal to a position of arm X₂ (i.e., equal to within a predeterminedtolerance). If the sensed X-level indicates that the position of arm X₁is higher than the position of arm X₂, control is transferred to step7040; if the sensed X-level indicates that the position of arm X₁ islower than the position of arm X₂, control is transferred to step 7050;and if the sensed X-level indicates that the position of arm X₁ is equalto the position of arm X₂, control is transferred to step 7060.

At step 7040 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to decrease voltage V_(X1) applied toelectronically-controlled, pressure regulator 1920 ₄, thereby decreasingpneumatic pressure to pneumatic actuator 1890 ₄ and relaxing test head6000 downward on the side of test head 6000 proximal to arm X₁.Electronic decision-making circuitry suitable for this purpose can befabricated in accordance with any one of a number of methods that arewell known to those of ordinary skill in the art. For example andwithout limitation, such electronic decision-making circuitry may befabricated utilizing logic circuitry, software controlled circuitry, ora combination thereof. Then, control is transferred to step 7070.

At step 7050 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to increase voltage V_(X1), thereby increasingpneumatic pressure to pneumatic actuator 1890 ₄ and urging test head6000 upward on the side of test head 6000 proximal to arm X₁. Then,control is transferred to step 7070.

At step 7060 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to set indicator i to i=1. Then, control istransferred to step 7070.

At step 7070 shown in FIG. 8, a Y-level is sensed by, for example andwithout limitation, a pattern of electrical contacts arrayed between asurface of test head 6000 and a work piece (not shown). Then, control istransferred to decision step 7080.

At decision step 7080 shown in FIG. 8, electronic decision-makingcircuitry in controller 6010 branches depending on whether the sensedY-level indicates that a position of arm Y₁ is higher than, lower than,or equal to a position of arm Y₂ (i.e., equal to within a predeterminedtolerance). If the sensed Y-level indicates that the position of arm Y₁is higher than the position of arm Y₂, control is transferred to step7090; if the sensed Y-level indicates that the position of arm Y₁ islower than the position of arm Y₂, control is transferred to step 7110;and if the sensed Y-level indicates that the position of arm Y₁ is equalto the position of arm Y₂, control is transferred to step 7100.

At step 7090 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to decrease voltage V_(Y1) applied toelectronically-controlled, pressure regulator 1920 ₃, thereby decreasingpneumatic pressure to pneumatic actuator 1890 ₃ and relaxing test head6000 downward on the side of test head 6000 proximal to arm Y₁. Then,control is transferred to decision step 7120.

At step 7110 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to increase voltage V_(Y1), thereby increasingpneumatic pressure to pneumatic actuator 1890 ₃ and urging test head6000 upward on the side of test head 6000 proximal to arm Y₁. Then,control is transferred to decision step 7120.

At step 7100 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to set indicator i to i=i+1. Then, control istransferred to decision step 7120.

At decision step 7120 shown in FIG. 8, decision making circuitry incontroller 6010 transfers control depending on the value of indicator i.In particular, if i=2 (indicating that test head 6000 is level in theX-direction and in the Y-direction), control is transferred to step7130; if i=1, control is transferred to step 7150; and if i=0, controlis transferred to step 7160.

At step 7130 shown in FIG. 8, controller 6010 sends signals to causeshut-off valves 1930 ₁-1930 ₄ in fluid channels 1570 ₁-1570 ₄ to beclosed, thereby locking test head 6000 in a leveled position. Then,control is transferred to step 7140.

At step 7140 shown in FIG. 8, the leveling process is finished.

At step 7150 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to set indicator i to i=0. Then, control istransferred to step 7020 to sense the X-level.

At step 7160 shown in FIG. 8, the electronic decision-making circuitrycauses controller 6010 to delay to allow more time for fluid to flow influid channels 1570 ₁-1570 ₄. Then, control is transferred to step 7020to sense the X-level.

In accordance with one or more embodiments of the present invention, amultiplicity of test heads may be leveled, and the test heads may bealigned, one to another. In particular, FIGS. 9A-9D show alignment andleveling apparatus 8000 which is fabricated in accordance with one ormore embodiments of the present invention for leveling and aligning fourindependent segments of test head 8010, the four segments 8010 ₁-8010 ₄being best illustrated in a top sectional view of alignment and levelingapparatus 8000 shown in FIG. 9D, which section is taken in a planeindicated by arrows G and G′ of FIG. 9C.

As indicated in FIGS. 9A-9D, each of segments 8010 ₁-8010 ₄ of test head8010 is supported on four balls (balls 8020 ₁-8020 ₄ are shown in FIGS.9A and 9C) wherein each of the balls rests on a movable wall (movablewalls 8030 ₁-8030 ₄ are shown in FIGS. 9A and 9C) of a correspondingfluid chamber (fluid chambers 8050 ₁-8050 ₄ are shown in FIGS. 9A and9C). In addition, in accordance with one or more embodiments of thepresent invention, each of segments 8010 ₁-8010 ₄ is secured in place bya bolt which is: (a) inserted through support plate 8100; (b) threadedinto the segment; and (c) held in tension by a Belleville spring (bolts8060 ₁-8060 ₂ and Belleville springs 8070 ₁-8070 ₂ are shown in FIGS. 9Aand 9C). In further addition, in accordance with one or more suchembodiments, the Belleville springs are designed to have a large dynamicrange such that the spring exerts a downward force on a test headsegment that is relatively constant over a typical range of verticalmotion of the test head segment. By way of example, a stack of two (2)Belleville springs may be used to provide a force that is within 10% ofthe maximum force over a range of motion of 500 microns. WhileBelleville springs may have desirable properties in that they may bedesigned to have a nearly constant force vs. displacement, otherattachment methods may be used including without limitation helicalsprings, cone springs, leaf springs, wave springs, magnetic holders,electromagnetic catches, and the like. In accordance with one or morealternative embodiments of the present invention, the ball supportsdisposed under each segment of test head 8010 may be replaced by any oneof a number of other suitable mechanisms such as, for example andwithout limitation, solid posts, wherein the posts are the means ofattachment of the segment to the array of movable walls of the fluidchambers, thereby eliminating a need for the bolt and the Bellevillespring as an attachment means.

As further shown in FIGS. 9A-9C, alignment and leveling apparatus 8000further comprises fluid chambers 8050 ₁-8050 ₁₆, each with a movable topwall, that are disposed in a surface of support plate 8100. As furthershown in FIGS. 9A and 9C, attachment bolts (attachment bolts 8060 ₁-8060₂ are shown in FIGS. 9A and 9C) are disposed in holes through supportplate 8100, wherein each bolt is preferably located under an areacentroid of a test head segment attached thereto. Further, as has beendescribed above, each of segments 8010 ₁-8010 ₄ of test head 8010 issupported on four balls (balls 8020 ₁-8020 ₄ are shown in FIGS. 9A and9C), wherein each of the balls rests on a movable wall (movable walls8030 ₁-8030 ₄ are shown in FIGS. 9A and 9C) of a corresponding fluidchamber (fluid chambers 8050 ₁-8050 ₄ are shown in FIGS. 9A and 9C). Inaddition, and in accordance with one or more such embodiments, the ballssupporting a segment of test head 8010 are arrayed around an attachmentbolt attaching the segment to support plate 8100. Thus, in accordancewith one or more such embodiments, each of the four segments 8010 ₁-8010₄ of test head 8010 are supported by interposition of four balls on fourmovable walls of four fluid chambers. In further addition, each ofsixteen fluid chambers fluid chambers 8050 ₁-8050 ₁₆ are each connectedby a fluid channel to central shut-off valve 8110. Whenever shut-offvalve 8110 is open (as shown FIG. 9A), fluid in each chamber is free toflow to other chambers.

A method for leveling each of segments 8010 ₁-8010 ₄ of test head 8010and aligning the segments, one to another, is best understood byreference to the cross-sectional view of alignment and levelingapparatus 8000 shown in FIG. 9A, and the top sectional view of alignmentand leveling apparatus 8000 shown in FIG. 9B, which section is taken ina plane indicated by arrows E and E′ of FIG. 9A. In accordance with oneor more embodiments of the present invention, during the leveling andaligning process, a controller (not shown) sends a signal toelectromagnetic mechanism 8130 (for example and without limitation, asolenoid) of shut-off valve 8110 is cause plug 8120 to be drawndownward, thereby opening fluid channels from each chamber to commonmanifold 8140 and enabling fluid in each chamber to flow to otherchambers via manifold 8140. Such a controller may be fabricated readilyby one of ordinary skill in the art utilizing, for example and withoutlimitation, any one of a number of commercially available programmablemicroprocessors, which microprocessors may be programmed routinely andwithout undue experimentation utilizing any one of a number of methodsthat are also well known to those of ordinary skill in the art. Inaccordance with one or more such embodiments, plug 8120 may have athrough-hole, from top to bottom, that allows fluid trapped in manifold8140 to relieve through plug 8120 as plug 8120 is drawn downward. Next,test piece 9000 is urged downward against electrical probes arrayed on atop surface of each of segments 8010 ₁-8010 ₄ of test head 8010 by adistribution of forces F. In accordance with one or more embodiments ofthe present invention, fluid flows in the fluid channels to equalizepressure in the fluid chambers. When the fluid pressure within all ofthe fluid chambers is equal, and the forces on each of segments 8010₁-8010 ₄ of test head 8010 are equal, segments 8010 ₁-8010 ₄ are inalignment. Then, shut-off valve 8110 is closed by having the controllersend a signal to release electromagnetic mechanism 8130, therebyallowing spring 8150 to move plug 8120 upward into manifold 8140,thereby closing off each of the channels leading from manifold 8140 to acorresponding fluid chamber. As the volume of fluid in each chamber isfixed when shut-off valve 8110 is closed, each of segments 8010 ₁-8010 ₄of test head 8010 supported by each chamber is locked in a levelposition by closing shut-off valve 8110.

Preferably, the fluid in the fluid chambers is relatively incompressibleso as to maintain the position of test head segments, notwithstanding avariable force transmitted to the test head segments by a test piece.More preferably, the fluid is a low vapor pressure liquid such assilicone vacuum pump oil supplied by Dow Corning. Alternatively, thefluid is selected from a group, for example and without limitation, ofhydraulic fluid, mineral oil, aliphatic oil, chlorinated hydrocarbonoils, Galden (available from Solvay Chemical), Fluorinert (availablefrom 3M Corporation), and the like.

As will be appreciated by one of ordinary skill in the art, theprinciples described above pertaining to various embodiments of thepresent invention may be used to design leveling and aligning apparatusthat disposes fluid chambers in various combinations. By way of example,each segment of a test head may be supported on movable walls of a firstset of fluid chambers in a first support plate. In turn, each of a groupof first support plates may be supported on movable walls of a secondset of fluid chambers in a second support plate. In addition, during aprocess of leveling and aligning segments of a test head, fluid may beallowed to flow between fluid chambers of a first set of fluid chambersby means of a first set of fluid channels; and fluid may be allowed toflow between fluid chambers of a second set of fluid chambers by meansof a second set of fluid channels. Further, when segments of a test headare level and aligned, fluid flow in the first set of channels may beshut off by one or more valves, and fluid flow in the second set ofchannels may be shut off by one or more valves, thereby locking segmentsof the test head in alignment.

Embodiments of the present invention described above are exemplary. Assuch, many changes and modifications may be made to the disclosure setforth above while remaining within the scope of the invention. Inaddition, materials, methods, and mechanisms suitable for fabricatingembodiments of the present invention have been described above byproviding specific, non-limiting examples and/or by relying on theknowledge of one of ordinary skill in the art. Materials, methods, andmechanisms suitable for fabricating various embodiments or portions ofvarious embodiments of the present invention described above have notbeen repeated, for sake of brevity, wherever it should be wellunderstood by those of ordinary skill in the art that the variousembodiments or portions of the various embodiments could be fabricatedutilizing the same or similar previously described materials, methods ormechanisms. Further, as is apparent to one skilled in the art, theembodiments may be used for making connections to semiconductor devices,electronic devices, electronic subsystems, cables, and circuit boardsand assemblies.

As one or ordinary skill in the art will readily appreciate, socketsfabricated in accordance with one or more embodiments of the presentinvention may include any number of fluid seals, gaskets, adhesives,washers, or other elements that function to seal the assembly and toprevent thermal transfer fluid from leaking (internally or externally).

The scope of the invention should be determined with reference to theappended claims along with their full scope of equivalents.

1. A method for aligning a first workpiece to a second work piece thatcomprises: placing the first workpiece on an alignment apparatuscomprising: (a) two or more fluid chambers disposed in fixed relation toeach other, the chambers having a movable wall and one or more aperturesfor admitting or releasing fluid; (b) fluid channels coupled to the oneor more apertures that enable fluid to flow between at least two of thefluid chambers; and (c) one or more valves disposed to enable or to stopthe flow of fluid through one or more of the one or more fluid channels;pumping incompressible fluid into the fluid chambers; opening the one ormore valves; bringing the first and second workpieces into contact;waiting a predetermined time for fluid flow in the fluid channels;determining whether the first and second workpieces are aligned; if theyare aligned, shutting the valves; and if they are not aligned, movingthe second workpiece a predetermined amount in a predetermineddirection, and returning to waiting.
 2. The method of claim 1 whereinthe chambers are disposed in a plate.
 3. The method of claim 1 whereinthe chambers are disposed in a plate and a test head is mechanicallyconnected to the movable wall of the chambers.
 4. The method of claim 3wherein the mechanical connection comprises one or more pillarsconnected to the movable wall of the chambers.
 5. The method of claim 3wherein the movable wall comprises a top surface of the fluid chambers.6. The method of claim 1 wherein the fluid channels are directed througha common junction.
 7. The method of claim 6 wherein the one or morevalves include a valve at the common junction.
 8. The method of claim 1wherein one of the one or more fluid channels is directed between a pairof fluid chambers.
 9. The method of claim 1 wherein the one or morevalves operate in response to a controller.
 10. The method of claim 1wherein: the two or more fluid chambers comprise three fluid chambers;the fluid channels comprise three fluid channels that each connect apair of fluid chambers; and the one of more valves comprise a valvedisposed in each of the three fluid channels.
 11. The method of claim 1wherein: the two or more fluid chambers comprise four fluid chambers;the fluid channels comprise two fluid channels that each connect a pairof fluid chambers; and the one of more valves comprise a valve disposedin each of the two fluid channels.
 12. The method of claim 1 wherein:one or more of the two or more fluid chambers has a movable wall thatcomprises a movable top surface.
 13. The method of claim 12 wherein themovable top surface comprises a diaphragm.
 14. The method of claim 1wherein: one or more of the two or more fluid chambers has a movablewall that comprises a movable bottom surface.
 15. The method of claim 14wherein: a mechanical connection between a test head and the movablebottom surface.